textproduct: Quad Cities

KEY MESSAGES

- There is a Marginal (level 1 of 5) risk for severe storms Tuesday. Primary threats will be damaging wind and locally heavy rain.

- Another stretch of quieter weather returns late in the week and into the weekend, with limited light precipitation chances.

SHORT TERM /THROUGH TUESDAY/

Issued at 205 PM CDT Mon Aug 17 2026

A much welcomed dry day, with more comfortable humidity levels was seen today compared to what we have seen in previous days! Early afternoon temps were in the upper 70s/low 80s, with dewpoints in the low to mid 60s (9 to 14 degrees cooler than 24hrs ago). GOES visible satellite imagery depicts a nice Cu field around 3-4kft across the entire area.

High pressure ridge to drift across the region late evening/early Tuesday providing clearing skies and quiet conditions. Some model guidance is beginning to show some fog potential, particularly east of the MS RVR closer to the ridge axis and where the boundary layer and soil moisture remain quite moist. Decided not to add any fog mention to the forecast just yet, but will pass on to the evening shift.

Tuesday...two weak shortwaves to track across the area providing enough lift and top down saturation to bring rain showers back into the forecast. The first wave to move across prior to sunrise and with the latest 17z RAP showing a 35kt LLJ developing, scattered showers with some embedded thunder will be possible during the morning hours. No severe storms are anticipated with this round. The question then becomes do we clear out and recover or does precip and clouds remain overhead for a good portion of the day thereby limiting heating. Latest CAMs remain mixed in their respective solutions regarding afternoon/evening storms along and ahead of the next shortwave and cool front. This leads to a lower confidence and conditional severe risk hinging on whether we see clearing take place. Our current forecast would favor clouds lingering longer in the morning, keeping our afternoon/evening severe risk limited. That said, if any differential heating/breaks in clouds can occur the kinematics are there for a few isolated severe low topped storms, albeit would like to see steeper mid-level lapse rates. Damaging wind and locally heavy rain would be the primary threats. The SPC Day 2 afternoon update has removed the Slight (level 2 of 5) out of the CWA, with the entire area now in a Marginal risk for severe (level 1 of 5). 0-3km shear is progged around 35kts and 0-3km CAPE around 150-200 J/Kg across the southern two tiers of counties, which would be the area to watch late afternoon/evening if storms were to form. With PWs around 2" once again, heavy rain will also be a concern and with such wet antecedent conditions south of I-80, WPC has a Day 2 Slight for excessive rain.

LONG TERM /TUESDAY NIGHT THROUGH MONDAY/

Issued at 205 PM CDT Mon Aug 17 2026

The storm system that moves across the area Tuesday into Tuesday night will usher in a pattern change to northwesterly flow across the Upper Midwest with ridging and a heat dome to our west and a trough over the eastern US. This places Iowa near the main storm track and in the transition zone to warmer temperatures to our southwest. This flow will lead to shortwave energy moving across the area every 36 to 48 hours with scattered showers and storms possible with each passing shortwave. Rain amounts are expected to be light with NBM probabilities of 0.5 inches or more below 10% through the period.

Tuesday night, a cool front is forecast to move southeastward across the area through 12 UTC Wednesday. The better lift is forecast to overspread the area after 00 UTC Wednesday. There is some disagreement between the different models on the amount of instability available after 00 UTC but 0 to 6km shear of 30 to 40 knots will be in place with the NBM mean CAPE of 1000 to 1500 J/KG of CAPE. There is also a similar signal in the HREF. Rainfall amounts will be light with most locations receiving less than a quarter of an inch. NBM probabilities of greater than a quarter of an inch are 10 to 15%. High pressure is forecast to quickly build into the area at the surface and aloft. This will bring quiet weather to the area

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 635 PM CDT Mon Aug 17 2026

VFR expected to prevail overnight into Tuesday. A round of scattered showers, with isolated/embedded thunder, is possible Tuesday AM into the early afternoon which could be accompanied by gusty W/SW winds (20+ kts). Confidence remains low on the coverage (20-50%), so have mentioned rain chances in PROB30s with this update. Redevelopment of scattered showers and storms are possible late Tuesday afternoon into the evening (20-50%); again confidence on coverage is low and therefore have not included in the TAFs yet.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.